Long-term immune effects of high-level natural radiation on Yangjiang inhabitants in China.

Purpose: Low dose radiation was found to perturb immune function or inflammatory reactions, which required further study. This study aimed to evaluate the health effects following long-term low dose radiation by detecting levels of peripheral blood lymphocyte subsets and serum cytokines of residents living in the Yangjiang High Background Radiation Area (HBRA). Materials and methods: Flow cytometry was used to detect peripheral blood T lymphocytes and its subsets (CD4 ⁺ T, CD8 ⁺ T lymphocyte) in 100 healthy female residents selected from HBRA and a Control Area (CA), respectively. Thirty cytokines or receptors and CRP levels were measured using antibody arrays in the 40 subjects described above. Subjects were chosen based on an age and BMI match between the two groups. Cytokine expression levels were then verified using ELISA methods. Result: In comparison to CA, CD8 ⁺ T lymphocyte numbers were significantly increased with cumulative dose following adjustment to age and BMI. Of the 30 selected targets, 22 indexes were measurable and inflammatory cytokines such as IFN-γ, IL-α, MCP-1, sIL-6R, EGFR, and CRP levels were observed to be significantly up-regulated with cumulative doses. ELISA results confirmed the cytokine array results and found CRP, MCP-1, and sIL-6R levels are linear with cumulative dose following adjustment to age and BMI. Conclusion: Immune function was found to be affected in humans exposed to long-term low dose radiation. Specifically, we observed an increase in CD8 ⁺ T lymphocyte numbers and an up-regulation of inflammatory biomarkers, including IFN-γ, MCP-1, sIL-6R, EGFR, CRP.